The Study Of Behavior

Leaf-cutter ants cut sections of leaves with their sharp mouthparts and head back to the nest with their load of leaf bits. In the nest, other individuals tend and harvest the fungi that grow on the leaves as food for the colony. Ethologists (ee-THAHL-uh-JlSTS), biologists who study behavior, seek to learn about such varied behaviors. Behavior is an action or series of actions performed by an organism, usually in response to a stimulus. In order to learn about behavior, etholo-gists ask questions about how and why a behavior occurs. For example, how do ants find their way to food and back to the colony? Why do ants share leaves with other colony members?

When considering an animal's behavior, ethologists ask four main questions: (1) What causes the behavior? What are the mechanisms that respond to stimuli? (2) What is the role of genes in the behavior; and how does it develop during an individual's lifetime? (3) What is the behavior's evolutionary history? (4) How does the behavior affect the organism's survival and reproduction?

Genes and Behavior

When studying behavior, ethologists often ask how much of an animal's behavior is determined by genetics and how much of the behavior is based on the unique developmental environment of the animal? Ethologists have studied bees to learn more about the role of genes in behavior. Some adult bees can detect which young in the hive have bacterial infections. These adult "hygienic" bees pull the diseased young from their cells and throw them out of the nest, as in Figure 44-1. In contrast, "nonhygienic" adult bees ignore diseased young.

American and Australian biologists mated hygienic queen bees to nonhygienic males and studied the inheritance pattern of this trait. They found that certain genes with set inheritance patterns control young-removal behaviors. This study showed that genes can underlie animal behavior. The triggers for the behavior, however, come from the environment. In this case, diseased young present in the hive trigger the removal behavior.

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